A radar apparatus that includes an array antenna as a reception antenna for receiving reflected waves of radar waves is conventionally known. This radar apparatus uses the phase difference in reception signals that occurs among reception antenna elements configuring the array antenna to detect the incoming azimuth of the reflected waves. The radar apparatus then detects the azimuth of a target that has reflected the radar waves on the basis of the detected incoming azimuth.
In the radar apparatus, the number of targets that can be detected can be increased by increasing the number of reception antenna elements configuring the array antenna. However, when the number of reception antenna elements is increased, the size of the reception circuit increases. This also leads to increase of cost. For example, the number of analog-to-digital converters configuring the reception circuit may increase. Further, the number of switching units may increase. The switching units are used for switching the reception signals of the plurality of reception antenna elements and inputting the reception signals to a single analog-to-digital converter.
On the other hand, according to another known technique, in a transmission antenna that emits radar waves, a plurality of transmission antenna elements are arranged in the same direction as that of the array of the reception antenna elements to apparently increase the number of reception antenna elements (e.g., refer to PTL 1).
According to this technique, as a result of arraying the plurality of transmission antenna elements in the same direction as that of the array of the reception antenna elements, a path difference from the emission point to the reception point can be created for the radar waves emitted from the respective transmission antenna elements. As a result, reception signal combinations are increased in a manner similar to that when the reception antenna elements are increased. According to this technique, the number of reception antenna elements can be apparently increased by two-fold by increasing, from one to two, the number of transmission antenna elements configuring the transmission antenna.